Tempering devices of this type represent the prior art. These devices operating using mixing valve technology are frequently used for tempering coolants, such as water/glycol mixtures, for example, for spindle cooling in machine tools, for cooling switch cabinets or hydrostatic drives, for cooling or tempering tasks in the printing industry, in laser technology, medical technology, and the like. Another field of application relates to the cooling of hydraulic fluids, for example, in connection with hydrostatic drives. In these systems operating using mixer valve technology, portions of the medium flowing back from the load in the return line pass through a 3/2-way valve in volumes dependent on demand for cooling capacity to reach a heat exchanger. The heat exchanger is in heat exchange with the evaporator of a cooling unit, and from there into the tank. A circulating pump, the pressure delivery side of which is connected to the feed line, sucks fluid medium from the tank and mixes it by a mixing device with the remaining medium, flowing back via the return line.